The present invention relates to automotive and vehicular heating systems, and more particularly, to an improved system for continuing the heating of an automotive or vehicular interior after the engine has been turned off.
In most vehicles having a water cooled engine a hot water circulation conduit or circuit is provided which uses the heated engine coolant to provide heat to the passenger compartment of the vehicle. When the engine is operating hot coolant from the engine is circulated through a heater core. A heater fan pushes air through the core, where it is heated by the hot engine coolant, and into the passenger compartment. It will be understood that the term heater fan is used herein to refer to the main fan or blower of a vehicle's interior heating, ventilating and air conditioning system.
In the past in order to keep a vehicle's passenger compartment warm, it was necessary to leave the engine idling, even if the vehicle was stationary or unoccupied. Only with the engine idling could hot coolant be pumped through the heater core. Such engine idling to keep the passenger compartment warm is a particular problem with police vehicles, taxi cabs, delivery trucks, utility trucks, or any other vehicle driven as part of an occupation requiring continuous or repetitive vehicle use together with periods of driver absence. Excessive idling causes unnecessary fuel consumption and air pollution.
In order to combat this problem after-run heaters have been developed for continuing the heating of vehicle interiors after the engine is turned off. After-run heaters rely on the fact that the engine coolant retains appreciable amounts of usable heat after the engine is shut off. Without an after-run heater that heat is dissipated to atmosphere and wasted. An after-run heater utilizes much of the coolant heat by transferring it into the passenger compartment. An example of such a heater is shown in Perhats, U.S. Pat. No. 4,308,994, the disclosure of which is incorporated herein by reference. A magnetically coupled pump with low battery drain, along with auxiliary control components, is utilized to circulate the still-hot engine coolant through the vehicle's heater core and to run the vehicle's heater fan while the engine is off.
In the most sophisticated, fully automatic systems, on-off seasonal switches, relays, temperature sensors and interconnecting wires are used to automatically sense if the engine is running, whether continued heating is necessary, and whether the engine coolant is warm enough to provide sufficient heat to the passenger compartment. Pump and heater fan operations are automatically terminated when the coolant temperature drops below a predetermined level and can no longer provide sufficient heat, thereby preventing unnecessary battery drain.
The system on-off, or "seasonal" switch may be left on throughout the heating season so that after-run control of the heating system is automatically provided each time the engine is turned off. Operation of the auxiliary heating system typically continues until one of the following four things happens: (1) the seasonal switch is turned off; (2) the ignition switch is turned on and the engine resumes control of coolant circulation; (3) the coolant temperature falls below a predetermined level; or (4) an optional timer times out. In each of these instances the engine cooling system and passenger compartment heating system return to normal and operate as if the after-run heating system were not present.
Known after-run heating systems have components located both in the passenger compartment as well as in the vehicle's engine compartment. Typically components such as the seasonal switch, indicator light and fan motor controls have been located in the passenger compartment inside or under the dash, while the engine coolant pump and temperature sensor have been located in the engine compartment. Prior systems required interconnection of these remote components by wiring. The need for installing wiring between the engine and passenger compartments makes installation of these systems difficult and time consuming for professionals and amateurs alike. Modern vehicles have no readily accessible openings in the fire wall between the two compartments through which wires may be passed.